A new high-pressure experimental apparatus to study magmatic processes at precisely controlled redox conditions

Abstract

Oxygen fugacity (fO 2 ) is typically controlled in high P-T experiments by using solid state redox buffer assemblages. However, these are restricted to impose discrete fO 2 values often with significant gaps between neighbouring assemblages. Semi-permeable hydrogen membranes (Shaw 1963) are often used in internally heated pressure vessels for more flexible fO 2 control in hydrous experiments; however, their implementation in more widely available externally-heated pressure vessels have not yet gained space. We propose a prototype Molybdenum-Hafnium Carbide (MHC) pressure vessel apparatus that simultaneously allows rapid quenching and flexible, precise, and accurate redox control via a custom-designed hydrogen membrane. Test runs with two membranes at a time, one imposing and another one monitoring fH 2 , demonstrated that 95% of the imposed hydrogen pressure was attained inside the pressure vessel within 2 hours at 800 -1000⁰C, after which a steady state equilibrium was established. Furthermore, This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.